V 2 5 = 



^V 2 3 



Mo 



<t 



t£ 



r' 





Jo 



/O 



•057 



•047 





tr. 



tr. 





none 



none 





•017 



•014 





008 



•007 





•003 



003 





•004 



•004 





Hillebrand — Vanadium and Molybdenum in Rocks. 211 



Table II. Component Minerals from certain of the above igneous rocks. 



Si0 2 V 2 5 =V 2 3 Mo 



No. Name and source. % % % % 



7 a . Amphibole from 7 ? -075 -062 none 



11*. Amphibole from 11 46 -044 -037 none 



2 l a . Pyroxene from 21... 51.5 -043 '036 



23*. Biotite from 23.. 36.5 -153 '127 none 



29 a . Amphibole from 29 50 -08 -066 



45 a . Biotite from 45... ? *057 -048 none 



46". Biotite from 46 35"5 -08 -066 



Table III. Miscellaneous. 



Si0 2 

 No. Name and locality of occurrence. % 



58. Epidotic schist, Mitchell Co., N. Carolina 48 



59. Quartz schist, Madera Co.. Calif 79 



60. Serpentine, Connecticut Valley, Massachusetts 38*5 



61. Sea green roofing slate, West Pawlet. Vermont 68 



62. Two red roofing- slates (equal parts), Washing- j 67 



ton Co., New York \ 56 



63. 253 sandstones 78'5 



64. 498 building limestones 14 



Of the igneous rocks specimens were so selected as to repre- 

 sent not only many widely separated localities, but also numer- 

 ous varieties from the least siliceous up to those high in silica, 

 in order to ascertain whether a preconceived opinion that the 

 vanadium accompanied chiefly the less siliceous rocks was well 

 founded or not. The choice was, however, confined largely 

 to those rocks analyzed in this laboratory within the past three 

 or four years of which a supply of powder remained after the 

 original analyses had been completed, and hence the list is 

 perhaps not fully representative. Nevertheless it permits of 

 drawing certain conclusions, the chief of which is that the 

 vanadium predominates in the less siliceous igneous rocks and 

 is absent or nearly so in those high in silica. The inference, 

 based on the existence of the mineral roscoelite, classed as a 

 vanadium mica, at once suggests itself, that the ultimate source 

 of the vanadium may be one or more of the heavier silicates 

 such as the biotites, pyroxenes, and amphiboles, and a few tests 

 on all the available mineral separation products lend strong 

 support to this view. For instance, the amphibole gabbros 7 

 and 11 show *038 per cent and "02 per cent V 2 3 , while the 

 amphiboles 7 a and ll a separated from them give '062 per cent 

 and -037 per cent; the pyroxenic gneiss 23 shows -083 per 

 cent against -127 from its contained biotite 23 a ; the diorite 

 29 with -031 per cent contains an amphibole 29 a with *066 per 

 cent; from -011 per cent in the quartz-mica diorite 45 and "012 

 per cent in the quartz monzonite -16 the percentages rise to '048 

 and *066 in their separated biotites 45 a and 46 a . The pyroxene 



